Electric switch



' Dec. 29, 1931. G. A. BURNHAM 1,839,083

ELECTRIC `swITpH Filed July 28, 1928 Patented Dec. 29,` 1931 UNITED-.P,a'rlgfflqf'l'i` Aenuncia: A. BURNHAM, or sUGUs, MASsAcHusETTs,

f OFFICE y AssIaNoa To coNDIT nr.ii;c :TnmALI 'MANUFACTURINGlCORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPORA-A i TIoN oFMASSACHUSETTS kELEcTaIc SWITCH l Application tiled 4July 28, 1928.`Serial No. 295,905.

This invention relates to electric switches or circuit breakers and hasparticular refer ence to the stationary and movable arcing contactmembers which cooperate to interrupt the current flowing through thecircuit. f f

Various devices have been employed to assist` in extinguishing thecircuit interrupting arc drawn between the separatingv contact members,but most circuit breakers depend primarily upon the quick separation ofthe contactrmembers themselves, whereby the arc is rapidlyV attentuatedand becomes so unstable that it goes out. vParticu-V larlyv in'oilimmersed ycircuit breakers, it is considered imperative that thel arcbe'extinguished as quickly as' possible since its presence in theoil-causes rapid decomposition rthereof into inflammable gases. andvvapors. Consequentlyit is the ractice to operate the movable switch memer with great rapidity either by gravity and inherent resihence of thelcontacts or by powerfulV acceleratingsprings associated with theoperating mechanism. "Particularly in the latter case, some means mustbe provided to absorb the energy of the movable switch member at the endof its opening stroke, and to this end resilient bumpershave beenprovided for the switch member, or decelerat-v ing springs havebeenlaced jin the .operating mechanism. The orrnerremedy l1s objectionabledue to therebound which tends to cause the reiestablishment of the arc,while the latter has a tendency to retard the switch member before thearc has been extinguished.

A circuit breaker is sometimes calledupon to interrupt a current manytimes its normal rating, due to a short circuit or some lother severevoverload condition, and the arc betweenk the `contacts may persist andcause thel destruction ofthe contacts. Particularly in the case of oilimmersed circuit breakers the damage may be very.' great due to thegeneration of Vinflammable oil gases and vapors, and a destructiveexplosion -may result from'a ersistence of the arc after the contactsare ully separated. c .y

\ It is an object of the present inventionto provide a circuit breakerwherein the 'sep-V i arable contacts are separated, preferably at thelatter part of the switch opening movement, and when the arc is alreadyattenuated and unstable, at a speed whichV is hi her than that of, andis due to, the speed o the movable switch memberthus to extin ui'sh anarc V.which might otherwisel persistl ora substantial period of time.

It is Va further object of the invention to providefmeans for utilizingthe surplus energy` of the movableswitch member. at `the end of itsswitch opening movement to enhance the extinguishment of the circuit`interrupting arc, and specifically toy utilize theenergy of themovableswitch member Y out appreciable rebound.

A still further object is generally to improve the construction andperformance Vof electric circuit breakers. ,y

Fig. l is av sectional. elevationl of an oil immersedl electric switchor circuit breaker embodying the invention. K

Fig. 2 is a sectional elevation of the switch taken onlines 2-2 of Fig;1.

Fig. 3 is a perspective view of the supporting bracket for the movablearcing contact members. i f Y l i Fig. l4r is a perspective view of acontact supporting arm for an arcing contact memf Fig. 5 is adetailshowing the springV assosupporting bracket of Fig. 3. As hereinshown, the electric switch lem,- bodying the invent-ion includes aswitch `ciated with Ythe contact arm of Fig. 4' and the frame 10 adaptedto provide a cover for the' vin which the cooperating stationary andmovable contact members of the switch are immersed.

Stationary switch members are supported by said switch frame 10 anddepend therebelow into the oil in said receptacle 12 and include theporcelain insulating bushings 14. which enclose axial conducting studs16. Said studs extend beyond the lower ends oil said bushings and arescrew-threaded at their lower extended ends into the stationary maincontact members or blocks 18.

Stationary auxiliary contacts or arcing members 19 are provided adjacentsaid main Contact blocks and are secured in conducting relation withsaid bloclr and held i'ixedly in position thereagainst by means ofscrews 19a.

The movable switch member includes the insulating switch opera-ting` rod2O which is adapted to carry the main and auxiliary movlable contactmembers at its lower end in position to engage the stationary main andauX- iliary Contact members 18 and 19 and complete the circuit throughthe switch. A metal rod 22, secured to said insulating rod 2O at itsupper end, is operatively connected to suitable switch operatingmechanism (not shown). At its lower end said rod 20 is provided with anenlarged portion 23, preferably ot metal, to which the main movablebrush Inember l24 is removably secured by means of a U-shaped metalclamp 25 having the upstanding ends 26 which are adapted to closelyreceive the laminations of the movable contact, or brush, 24therebetween. A pin BO extends through the upstanding vends 26 of saidU-shaped clamp and the enlarged portion 23 of said switch operatingrmember whereby said brush is removably secured to said operating rod 20,and fasteners 32 serve to secure the laminations oi'v the brush orbridging member 24 to the bottom of said U- shaped clamp 25.

The U-shaped clamp 25 is further provided with opposed outwardlyanddownwardly extended arms, or brackets, 34, Fig. 3, which are arrangedto support the movable auxiliary contact or arcing members therebeneath.To this end said arms Set are each provided with a pair of spaceddepending ears 36 at their free outer' ends upon which contactsupporting frocker arms 38 of the auxiliary contact members arepivotally supported by pins Ll0. As shown in detail in Fig. l, saidcontact supporting arms 38 are of channel section and are provided withsupporting ears Ll2 intermediate their ends by whi-ch they are pivotallysupported on the pins Zl() between the ears 3G of said brackets 34.Contact or arc- ,ing members 14 are secured detachably by screws 47 tothe outwardly directed upturned ends 118 of said supporting arms 3S inposition to cooperate with the stationary contacts 19.

Said arms 38 Vare further provided Withintegral inwardly extended arms50 the upturned ends of which are disposed side by side or overlap eachother at a point beneath the middle of said U-shaped clamp 25. Said armsi0 preferably have struck out portions 5l at their overlapping ends asshown in Figs. 2 and d, so that both arms are free for vertical movementwithout interference trom the other.

Means are provided constantly to bias said contact supporting arms 38 inan upward direction against the ends 52 of the brackets 34, which act asabutments to limit the upward movement of the arcing contact members. vSaid means comprise the constantly stressed cantilever springs Sil whichencircle the pins 40, one end of each spring passing through said .pins4() and the other end eX- tending beneath and bearing against an arm 8S,as shown in Fig. 5. The movable arcing contact members 44 areconsequently urged against their cooperating contacts 19 when the switchis in closed position, and due to the above resilient support are causedto remain in contact therewith for a sufficient time subsequent to theseparation of the main brush member 24.- to prevent arcing at the maincontacts and brush members.

Then the operating rod 20 is moved downwardly to open the switch, an arcis drawn between each pair of auxiliary contact members 19 and 14 and itattenuated by the downward movement ol the movable switch member, theopening speed of which is enhanced by an accelerating spring 45,surrounding the rod 22. Under normal conditions'the arc will becomeunstable and go out before the movable switch member has reached the endof its opening stroke, but under heavy overload conditions the arcbetween the auxiliary contacts 19 and 44 may persist after the movableswitch member has reached the end ot opening stroke and may, unlessextinguished, cause the destruction ot' the switch.

According to the invention, means are provided to eiiect, during thefinal opening movement of the switch member, an extent of separation ofthe arcing members which is greater than the stroke of the movableswitch meinber, and a speed of separation which is materially greaterthan the speed o opening movement of the movable switch member. To thisend a resilient bumper provided directly beneath and in axial alignmentwith said movable operating rod 20, which bumper is arranged to engagethe tips of the inwardly directed overlapping arms 5() of said contactsupporting arms 3S prior to the end of the opening stroke of the movableswitch member.` `Said bumper as here shown includes a piston 5G havingan upstanding stem 58 which is axially aligned with the operating rod2()and hence directly beneath the adjacent struclr-out ends of `arms 50, anenclosing casing 60 for said piston, and a helical compression spring 62disposed within said casing'beneath'said piston and in positionconstantlyto bias said piston in an upward direction. -Said casing issuitably supported in fixedposition ras byv being secured by bolts64f`to andbeneath a cross vbar'66 whichfextendsacross the centre of theswitch casing 12 perpendicular to the bridging member `24.V

Uprights 68 preferably of insulating material extendy upwardlyfrom saidcross-bar in position to be secured removably by boltsV 70 toa pair ofsuitably spaced depending ears 72 whichmay be formed integral with theswitch frame 10.` y

As the movablefswitch member nears the end of its switch openingmovement, the arms -engage the stem' 58, and sincethe spring 62 beneaththepiston 56 is relatively stitfcompared Awith the springs 54 of theauxiliary contact members, the springs 54 yield the most andcause thecontact supporting arms 38 to rotate about pins 40 to effect a Afurtherand rapid separation of the arcing contacts towards the lower Vdottedline position of F ig. 1. The spring 62 is initially compressed uponthe' engagement of the stem 68 and arms 50 and absorbs enough of theenergy'of the switch opening movement to prevent injury to themechanism, and reacts immediately to continue the downward and outwardmovement of the movable arcing tips 44.

It will be noted Athat during the opening movement of the switch intothe intermediate dotted position of Fig. 1, 'prior tothe engagement ofthe stem 58 with the arms 50, the arcing members 44 are moved inauniform vertical path away 'from their cooperating contacts 19, whilethe subsequent movement ofthe'contacts 44 due to the pivotal movement ofarms 38 about their supporting pins 40, is at an Vangle to this path andto y the axis of the existing arc. lThe location of the pivot pointslof' the contactv supporting members `38 is such that a Asmall linearmovement of the arms' 50 causes a considerably greater linear movementof the outer arms 48 on which' the arcing contact members are carried;so that the rapidniovement of the movable switch member against thebumper, due to the accelerating spring and the force of gravity, causesthe arcing tips to be moved downwardly through'the oil'suddenly and atan angle to the axis of the existing arc into the lower dotted positionof Fig. l', and any arc whichy may have persisted willbe caused to goout, the arcing member 44 being snapped away from the-foot of the arc aswell `as being laterally displaced therefrom' in the he work performedin moving the Contact bearing arms 38 suddenly through the 'oil againstthe bias of springs 54 is considerable and consequently the force of themovable switch member is'dissipated without'any l'appreciable reaction.The spring 62 beneath the piston serves largely to protectthe movablethe stem 58 andbeing relatively rigid will react before the end oftheswitch opening l stroke of the switch member. v

f The uprights- 68 which support the bumper are arranged to bevertically adjustable to var-y the point in the switch opening movementat which the bumper will operate to snap the, arcing 'contacts apart. Tothis end a series of vertically aligned holes 7 4 are'pro- `vided in theuprights 68through any of which the bolt 7 0 may be inserted.

Although I have disclosed the invention 'as embodied in an oil immersedelectric switch it is equally applicable to air-break switches andvarious modifications in the structure may be ade without departing fromthe scope of this invention.

Iclaimz' Y H 1. In `an electric switch,fthe combination of a stationaryswitch member, a movable switch member having an arcing member which ismovable therewith' and which'cooperateswith saidV stationary switchmember, and means effective only during the later part of the opening`movement ofthe movable switch member and after said arcing member hasbeen moved at the velocity of opening movement of'saidmovable switchmember a substantial distance out of engagement with said stationaryswitch member to move said arcing member further in a direction awayfrom said stationary switch vmember at a rate of speed which is greaterthan the opening speed of said arcing member due to the speed ofsaidmovable switch member. Y .2.: The method of interrupting an electricarc which consists in initially elongating it at a suitablerate and`then in suddenly elongating it at a materially increased rate.

3. The method of interrupting an electric yarc which consists inelongating itat a suitable rate until it becomes unstable and thereuponcontinuing its elongation at a materially increased rate. Y

4. In an electric switch, the combination of a stationary switchmember,v a movable switch member, a pivotally mounted arcing membercarried by themovable switch member and engageable and disengageablewith said stationary switch member, and means cooperating with saidmovable switch member and effective onl after the karcing member hasmoved a su stantial distance away fromsaid stationary switch member torotate said arcing member ab'outits pivot in aswitch opening directionduring and by the switch opening movement of they switch. 5. In anelectric switch, the combination of a pair of stationary switch'members,a movable switch member, a pair of pivotally switch opening speedthereof out of engagement, with and into a position remote from saidstationary switch member, and means cooperating with said movable switchmember near the end of its switch opening movement constructed andarranged to engage said movable switehmember and rotate said areingmembers about their pivots in a switch opening direction during thefinal switch opening movement ot' said movable switch member and at aspeed greater than the speed of said arcing members due to the openingspeed of said movable switch member.

6. In an electric switch, the combination of a switch member which ismovable between switch open and closed positions, a stationary switchmember, an arcing member pivotally carried by said movable switchmember, and means operated by the opening movement of said movableswitch member to engage and move said arcing member about its pivot in aswitch opening direction only during the final part of the switchopening movement.

7. In an electric switch, the combination of a movable contact member, astationary contact member, an auxiliary contact supporting arm carriedby said movable contact member and movable in respect thereto, an arcingmember carried by said arm, and means normally operatively free Jfrombut engageable with said arm during the linal part only of the openingmovement of said movable contact member to move said arcing member in aswitch opening direction and at a speed in eX- cess of the speed oi saidarcing member due to the opening speed of said movable contact member.

8. In an electric switch, a stationary switch member, a cooperatingmovable switch member, means to separate said members at a given rate,and other means operative after said members have been separated a givendistance to increase the rate of separation of said switch members.

9. In an electric switch, a stationary switch member, a cooperatingmovable switch member having a pivotally supported arcing tip movablebetween switch open and closed positions, and means disposed in theswitch opening path of movement of said movable switch member andnormally operatively free from said switch member arranged to engage androtate said moving arcing tip about its pivotal support in a switchopening direction only after said arcing tip has moved a given distance.

10. In an electric switch, a stationary switch member, a cooperatingmovable switch member, an arcing contact member having a movable supporton said movable switch member and movable therewith into and out ofswitch clos-ing position, and a relatively fixed abutment normallyoperatively free from and disposed in the switch opening path of`movement of said movable switch member in position to engage and movesaid arcing contact member about its movablesupport in a switch openingdirection during the final part of movement only of said movable switchmember.

11. In an electric switch, a movable switch member including a switchoperating rod, and a pivoted contact member movable therewith into andout of switch closing position, and a resilient bumper disposed beneathsaid movable switch member in position to engage said contact member'and rotate it about its pivotal support in a switch opening directionduring the movement of said switch member int-o switch open position.

l2. In an electric switch, the combination of a movable switch memberincluding a reciprocable switch operating rod, a main Contact memberdisposed at the lower end of said rod, a downwardly and outwardlyextended bracket carried by the lower end of said rod, a contactsupporting member pivoted to the extended end of said bracket and havinga relatively long contact supporting arm and a short striker arm, anarcing tip carried at the extended endofsaid Contact supporting mem*her, and a relatively fixed abutment disposed beneath said movableswitch member in position to engage said striker arm at the end of theswitch opening movement of said movable switch member.

i3. In an electric switch, the combination oiE a movable switch memberincluding a reciprocable switch operating rod, a main contact memberdisposed at the lower end of said rod, a downwardly and outwardlyextended bracket carried by the lower end ot said rod, a contactsupporting member pivoted to the extended end of said bracket and havinga relatively long contact supporting arm and a short striker arm, anarcing tip carried at the extended end of said contact supportingmember, and a relatively fixed abutment disposed beneath said movableswitch memller in position to engage said striker arm at the end ot theswitch opening movement ot' said movable switch member whereby saidarcing tip is snapped downwardly and outwardly by the rotation of saidcontact supporting arm about its pivotal support on said bracket.

lll. In an electric. switch, the combination oi" a pair of spacedstationary switch members, a movable switch member cooperatingtherewith, al pair or' pivotally mounted arcing contact members carriedby said movable switch member, and means to prevent a rebound of saidmovable switch member at the end of its switch opening movement includaresilient abutment disposed in thel path of movement thereof and inposition tov engage and move said arcing contact members rapidly abouttheir pivotal. support in a switch opening direction, whereby to absorbthe energy of switch opening movement oit' said movable switch member.

15. The method of interrupting an electric circuitV which consists indrawing an arc, attenuating the arc until the arc reaches a stage whereit becomes unstable, and causing Athe arc to go out by suddenlyincreasing the rate of attenuation of the arc.

16. The method of interrupting an electric circuit which consists indrawing an arc between two cooperating contact members, separating saidcontact 'members substantially in a straight line to attenuate the arcand cause it to become unstable, and subsequently causing one of saidcontacts to move Y suddenly further away from its cooperating Contactmember and at an angle to the previous line of separating movementthereof.

17. The method of interrupting an electric circuit which consists inestablishing an arc in an arc quenching fluid, attenuating said arcslowly in a uniform path until said arc becomes unstable, and thenrapidlyy attenuating said arc and simultaneously displacing laterally ofsaid path in the arcquenching uid.

18. The method of interrupting an electric switch which consists inestablishing an arc between two cooperating arcing Contact members andbeneath an arc quenching fluid, drawing the arc out by separating saidcontact members ina uniform path, and finally moving one of said contactmembers with a snap action at an angle to. said first path of movement,whereby to further attenuate the are and also to snap said contactmember lat-v erally away from the foot of the arc.

19. The method of operating an electric switch of the type having amovable switch member and an arcing member movable on said switchmember, which consists in arrestingthe opening movement of the movableswitch member in the latter part only of its switch openingmovement andutilizing the energy thereof in moving the arcing member in a switchopening direction.

20. In an electric switch, engageable and disengageable Contact members,andrmeans to separatel the disengaged contact members at a given rateincluding means effective only after a given extent of separation tosuddenly increase the rate of separation of said contact members.

In testimony whereof, I have signed my name to this specification.

GEORGEV A. BURNHAM.

